Multichannel catheter

ABSTRACT

A single, multichannel catheter is useful for extracorporeal circulation of blood to a patient undergoing cardiovascular treatments or surgery. The catheter has three independent channels and an expandable balloon at one end of the catheter. The first channel is largest and allows for delivery of blood to a patient in an amount sufficient to maintain the patient&#39;s metabolism and perfusion throughout the treatment or surgery. The second and third channels are smaller and integrated into the wall of the first channel. The second channel is for delivering a biologically active fluid to the heart and/or venting the left heart. The third channel is for delivering a fluid to the balloon for its expansion when positioned in the ascending aorta to occlude the flow of blood to the heart. One or more perfusion openings may be located in the descending aorta.

CROSS-REFERENCE

This is a continuation of U.S. Ser. No. 08/766,384, now U.S. Pat. No.5,868,703 filed Dec. 6, 1996, which in turn is a continuation-in-part ofprovisional application U.S. Application No. 60/014,922, filed Apr. 10,1996.

FIELD OF THE INVENTION

This invention relates to a multichannel catheter for use in conjunctionwith cardiovascular examinations, treatments and surgery. It alsorelates to methods for making and using such a catheter.

BACKGROUND OF THE INVENTION

To better understand the background and problems faced by those of skillin this area of technology it is useful to understand the basic workingsof the heart and circulatory system. The following discussion refers toschematics of the heart shown in FIGS. 1 and 2.

The human heart is a muscular pump having four separate cavities and aseries of valves allowing blood to pass in one direction only. Mammals,including humans, have a double circulatory system. Blood that hasreleased oxygen to the tissues (9 and 14) and has absorbed carbondioxide from them (venous blood) is returned to the heart through thesuperior and the inferior venae cavae (11 and 10). This blood enters theright auricle (3), whose contractions cause the blood to pass throughthe tricuspid valve (16) in the right ventricle (1). The contractions ofthe right ventricle pass the blood through the pulmonary semilunarvalves (17) and along the two pulmonary arteries (5) into the lungs (6).In the lungs, the blood is oxygenated and returns to the heart throughthe pulmonary veins (7) and thus enters the left auricle (4). Thischamber contracts and passes the blood through the bicuspid, or mitral,valve (15) into the left ventricle (2), whose contractions force theblood through the aortic semilunar valve (18) into the aorta (12 and13), which is the biggest artery of the body and to other parts of thebody through, i.a., the great arteries 8.

Thus the right side of the heart serves mainly to pump deoxygenatedblood through the lungs, while the left side pumps oxygenated bloodthroughout the rest of the body. This is represented as a flow schematicin FIG. 2, where similar numbers refer to similar parts of the heart.The heart varies the output by varying the volume of blood admitted intothe ventricles each time the latter are filled and also by varying therate of contraction (faster or slower heartbeat). The left side of theheart (left auricle and ventricle) has to circulate the blood throughall parts of the body, except the lungs, and has thicker and morestrongly muscular walls than the right side, which has to perform thepulmonary blood circulation only. For proper functioning, the left sideand the right side must be accurately interadjusted, both with regard tothe contraction rate of the respective chambers and with regard to theoutput of blood. When functional disorders of the heart occur, it may benecessary to examine the heart to determine the problem and possiblyperform surgery or provide treatment.

In performing examinations or treatments of a subject's heart, orperforming surgery on the heart, it is often necessary to reduce therate at which it normally beats or stop its beating completely. Thisallows a physician to observe, or operate on, the heart more easily.However, by reducing or stopping the heart rate (i.e. cardioplegia),blood will not be adequately circulated to the rest of the body. Thus,it is generally necessary to circulate the blood using some type ofextracorporeal blood circulating means that regularly circulatesoxygen-rich blood through the arteries, collects oxygen-depleted bloodreturning through the veins, enriches the oxygen-depleted blood withadditional oxygen, then again circulates the oxygen-rich blood.

The types of examinations, treatments and operations that require somedegree of cardioplegia or drug delivery and extracorporeal bloodcirculation include open heart surgery and less-invasive heart surgeryto perform single or multiple coronary artery bypass operations, correctmalfunctioning valves, etc. Others include, but are not limited to,myocardial revascularization, balloon angioplasty, correction ofcongenital defects, surgery of the thoracic aorta and great vessels, andneurosurgical procedures.

The extracorporeal blood circulation generally requires the use of sometype of heart-lung machine, i.e. a cardiopulmonary machine. This has thethreefold function of keeping the replacement blood in circulation bymeans of a pumping system, of enriching with fresh oxygen the blood oflow oxygen content coming from the patient's body, and regulation ofpatient temperature. The system shown in FIG. 3 diagrammaticallydescribes the manner in which such a machine works.

The venous blood, before it enters the right auricle of the heart isdiverted into plastic tubes (20), generally by gravity flow. The tubesare positioned to receive the blood from the superior and inferior venaecavae (shown as 11 and 10 in FIG. 1). This blood, which has circulatedthrough the body and consequently has a low oxygen content is collectedin a reservoir (21). A blood pump (22) is used to pump the blood througha heat exchanger (23) and artificial lung (24). The heat exchanger (23)and artificial lung (24) may be one of several designs to regulate bloodtemperature and increase the oxygen content of the blood. Modern designsuse advanced membrane technology to achieve the oxygenation, which issimilar to the way red blood cells absorb oxygen from the human lung.The oxygenated blood then passes through a filter (25) and is returnedto the patient. Losses of blood occurring during the course of theoperation are compensated by an additional blood reservoir (26).Collected blood is passed through a defoamer (27) and is likewise passedto the to the reservoir 21, heat exchanger (23) and artificial lung(24). Before starting the cardiopulmonary bypass machine theextracorporeal circuit is filled with one or two liters of salinesolution.

In circulating the oxygenated blood to the body from filter 25, it canbe pumped through a catheter 28 by inserting the catheter into the aortaor one of its major branches and pumping the blood through the catheter.However, when the heart is to be operated on, it must be free of bloodand sometimes the heart beat must be reduced or stopped completely.Referring again to FIG. 1, blood is prevented from entering the heart byblocking the ascending aorta 12 near the semilunar valve 18 while at thesame time preventing blood from entering the right auricle 3 bywithdrawing blood through the superior vena cavae 11 and inferior venacavae and 10. Blocking the ascending aorta may be achieved by clampingor preferably by balloon blockage. At the same time that blood isprevented from flowing through the heart, a cardioplegia solution isadministered locally to the heart to arrest the heart. Thus, there is aneed for a device that allows a heart specialist to locally administercardioplegia to the heart, block the flow of blood to the heart, whileat the same time circulating oxygenated blood to the patient's body,particularly through the great arteries (8 in FIG. 1), to ensure alllimbs and tissues remain undamaged during the heart examination oroperation.

Several devices are described in the literature to address the need foran appropriate device. One example is disclosed in U.S. Pat. No.5,312,344 issued 17 May 1994 to Grinfeld et al. This patent describes amultichannel catheter having at least three passageways, one of which isused for blood circulation and another is used for cardioplegiatransportation. The third is used to transport fluid to an inflatableballoon which is located at the distal end of the catheter and is usedto block the ascending aorta. The channel for blood is described ashaving outlets on the downstream side of the balloon to allow blood tobe circulated to the body tissues. The design of this multichannelcatheter shows that either each passageway is a tube encased in acannula or the smaller passageways are located within the largerpassageway for cardioplegia solution or blood. Thus, the smallpassageways are not integral with the walls of the blood-carrying tube.Also, there is no teaching of the importance of the large volume neededfor the blood-carrying catheter.

Another example can be seen in U.S. Pat. No. 5,433,700 issued 18 Jul.1995 to Peters. This patent describes a process for inducingcardioplegic arrest of a heart which comprises maintaining the patient'ssystemic circulation by peripheral cardiopulmonary bypass, occluding theascending aorta through a percutaneously placed arterial ballooncatheter, venting the left side of the heart, and introducing acardioplegia agent into the coronary circulation. As part of thedisclosure a multichannel catheter is disclosed which provides channelsfor the cardioplegia solution, a fluid transportation to inflate theballoon and a lumina for instrumentation. However, there is nodescription in the patent of a multichannel catheter which is designedto administer cardioplegia solution, inflate a balloon, and providecirculation of blood all using the same multichannel catheter. ThePeters process teaches the use of a separate catheter to deliveroxygenated blood to the body while a heart is stopped.

Another example of a device is found in U.S. Pat. No. 5,478,309 issued26 Dec. 1995 to Sweezer et al. This is a rather complex device andsystem of venous perfusion and arterial perfusion catheters for use inobtaining total cardiopulmonary bypass support and isolation of theheart during the performance of heart surgery. One of the multichannelcatheters described in the patent for delivering cardioplegia solutionto the heart while blocking the ascending aorta and circulating perfusedblood. This catheter requires a cannula having two passagewaystherethrough. In the first passageway another slidable cannula havingtwo passageways through it and having a passageways for guidewires arepositioned. These passageways are for delivering a fluid for inflatingthe balloon at the distal end of the catheter and cardioplegia solutionto the heart to stop its beating. The second passageway through thecannula used for transporting blood that has been oxygenated by thecardiopulmonary machine. However in this particular design no discussionof the need to maximize the flow of blood and minimize the damage to theblood components is discussed. Thus the volume of the two passageways isabout the same.

Another device is described in U.S. Pat. No. 5,458,574 issued 17 Oct.1995 to Machold et al. It shows a multichannel catheter which haschannels for fluid to blow up balloons for blocking the aorta, a channelfor cardioplegia solution and a channel for instruments for examiningthe heart. Nothing in the patent describes a multichannel catheter ofapplicant's design.

Still another patent, U.S. Pat. No. 5,452,733 issued 26 Sep. 1995 toSterman et al. No details are given in that patent of the design of thecatheter that might be used.

Still another patent application filed as PCT/US 94/09938 havinginternational publication No. WO95/08364 filed 1 Sep. 1994 in the nameof Evard et al. describes an endovascular system for arresting theheart. This too lacks any detailed description of a multichannelcatheter that could be used in the manner described in the instantapplication.

PCT International Application number PCT/U.S. Pat. No. 94/12986published as Publication No. W095/15192, filed 10 Nov. 1994 in the nameof Stevens et al. provides a description of a partitioning device thatis coupled to an arterial bypass cannula. The description provides forthe cannula to be introduced to the femoral artery where thepartitioning device has a balloon at the end of the flexible tube toblock the ascending aortic artery and allow blood to circulate through alumen.

While the above devices address in part the needs of the art, it hasbeen discovered that certain problems exist that must be furtheraddressed to maximize the efficiency of the device and cardiopulmonaryoperations. The first problem is ensuring maximum flow of blood throughthe device (which must be of a diameter sufficiently small to fit into apatient's femoral artery) so that the tissues receive enough nourishment(i.e. oxygen, etc.). We have found that by ensuring that (1) the channelfor blood is at least 70% of the available volume and (2) the channelfor blood is clear of an other tubes or obstructions, the blood flow ismaximized. Another problem is ensuring that the blood components are notinjured by excess flow rate and sheer stress in the circulation process.We have found that by providing strategically located blood outlets thatare preferably elongate in shape the sheer stress is reduced. Anotherproblem is ensuring the blood flow to the great arteries is maximized toavoid damage to the tissues, particularly the brain. We have foundtissue damage is avoided by ensuring the blood circulating outlets arelocated on the catheter such that when the catheter of this invention isin place, the outlets are located adjacent to the great artery openings.Finally we have found that by using extrusion molding techniques themultichannel catheter of this invention is prepared so that (1) theblood-carrying passageway is at least about 70% of the available volumeand (2) the other passages account for less than about 30% of theavailable volume and are integral with the wall of the blood-carryingpassageway, the blood flow problems are minimized.

OBJECTS OF THE INVENTION

An object of this invention is to provide a unique multichannel catheterhaving multiple uses.

Another object of this invention is to provide a unique multichannelcatheter useful in examinations of and surgical operations on a mammal'sheart.

Another object of this invention is to provide a unique multichannelcatheter useful for efficiently delivering oxygenated extracorporealblood through a major channel of the catheter to supplement or replaceblood from the mammal's heart.

Another object of this invention is to provide a unique multichannelcatheter that maximizes the rate of blood flow through the catheter'sblood passageway while minimizing the outside diameter of the catheter.

Another object of this invention is to provide a unique multichannelcatheter that reduces the sheer stress on the blood pumped through thecatheter's blood passageway for delivery to the mammal's arterialsystem.

Another object of this invention is to provide a blood circulatingcatheter that provides improved peripheral circulation and perfusion.

Another object of this invention is to provide a process for preparing aunique multichannel catheter by extrusion molding.

Another object of this invention is to provide an improved process forperforming surgery on a mammal's heart.

Another object of this invention is to provide a unique multichannelcatheter that is useful in both open chest and least invasive heartsurgery.

It is another object of this invention to provide improvements in themanagement and treatment of coronary heart disease.

It is another object of this invention to provide for easy positioningof a unique multichannel catheter through insertion into a major branchof the aorta such as the subclavian or femoral artery to locate thedistal end of the catheter in the ascending aorta of the mammal andprecise placement of the balloon.

SUMMARY OF THE INVENTION

One aspect of this invention is a single, multichannel catheter usefulfor extracorporeal circulation of blood to a patient undergoingcardiovascular treatments or surgery. The catheter has three independentchannels and an expandable balloon at one end of the catheter. The firstchannel is the largest and is of a size that allows for delivery ofblood to a patient in an amount sufficient to maintain the patient'smetabolism and perfusion throughout the treatment or surgery. A secondchannel, smaller than the first, is integrated into. the wall of thefirst channel and is suitable for delivering cardioplegia fluid to theheart and/or venting the left heart. A third channel, also smaller thanthe first, is integrated into the wall of the first channel and suitablefor delivering a fluid to the balloon for its expansion when positionedin the ascending aorta to occlude the flow of blood to the heart.

Another aspect of this invention may be viewed as an improved method ofperforming cardiovascular surgery on a patient using a cardiopulmonarymachine for extracorporeal circulation of blood. The improvementcomprises using the catheter of this invention to deliver blood to thepatient, provide cardioplegia fluid to the heart, occlude the flow ofblood to the heart, and vent the heart if needed.

Another aspect of this invention is the multichannel catheter whereinthe large first channel (i) extends substantially the length of thecatheter, (ii) comprises at least about seventy percent of the availablechannel volume of the catheter, (iii) is defined by the wall of thecatheter, and (iv) is closed at its distal end. The second channel (i)extends substantially the length of the catheter parallel to said firstchannel but independent thereof, (ii) is integrated into the wall of thefirst channel, and (iii) is open at its distal end. The third channelextends substantially the length of the catheter parallel to the firstand second channels but independent thereof. The third channelcomprises, in combination with the second channel, not more than aboutthirty percent of the available channel volume of the catheter, isintegrated into the wall of the first channel and spaced from the secondchannel, and is closed at its distal end. In the wall of the catheternear the distal end of the catheter and communicating with said firstchannel are a plurality of openings. The balloon means is integratedinto the distal end of the catheter downstream from the first channelopenings but upstream of the second channel distal opening andcommunicates with the third channel through an opening in the wall ofthe catheter. The catheter is of a size suitable for insertion into ablood vessel of a mammal and is for use in conjunction withcardiovascular examinations and surgery. Preferably the plurality ofopenings communicating with the first channel are elongate with thelength of the openings being parallel to the length of the catheter andthe first channel is large enough to transport oxygenated blood therethrough from the proximal end to the distal end.

Another aspect of this invention is a process of preparing the precursorto the multichannel catheter described herein, which process comprises

-   -   (A) Extrusion molding a catheter having distal and proximal ends        wherein the catheter comprises    -   (1) a central, first channel (a) extending substantially the        length of the catheter, (b) comprising at least about seventy        percent of the available channel volume of the catheter, and (c)        being defined by the wall of the catheter;    -   (2) a second channel (a) extending substantially the length of        the catheter parallel to said first channel but independent        thereof and (b) being integrated into the wall of the first        channel;    -   (3) a third channel (a) extending substantially the length of        said catheter parallel to the first and second channels but        independent thereof, (b) comprising, in combination with the        second channel, not more than about thirty percent of the        available channel volume of the catheter, and (c) being        integrated into the wall of the first channel and spaced from        the second channel. Other steps are taken to complete the        catheter, as discussed hereinafter.

Another aspect of this invention is a process for providing oxygen-richblood to a subject's arterial circulation and providing cardioplegiasolution to the heart of the subject to arrest the heart and minimizedamage to the heart. The process comprises

-   -   positioning the multichannel catheter, as described        hereinbefore, in the ascending aorta;    -   providing a source of oxygen-rich blood to the proximal end of        the first channel of the catheter;    -   providing a source of cardioplegia fluid to the proximal end of        the second channel of the catheter;    -   providing a source of fluid for inflating the inflatable means        to the proximal end of the third channel of the catheter;    -   positioning the multichannel catheter within the subject's blood        circulatory system such that (a) the distal end of said catheter        is positioned in the ascending aorta and the first channel        openings are located proximate the great arteries, (b) the        inflatable means is located on the cephalid side of the aortic        valve, and (c) the distal end of the second channel is located        proximate the aortic valve and downstream of the inflatable        means;    -   inflating the inflatable means to block the flow of blood to the        heart;    -   pumping cardioplegia solution into the heart to arrest the        subject's heart rate;    -   pumping oxygen-rich blood through said first channel out the        first channel openings at rate sufficient to maintain the        subject's metabolism and perfusion;    -   performing a surgical operation on the heart as needed; and    -   maintaining circulatory support of said subject as needed.

Other aspects of the invention will be apparent to one of skill in theart upon further reading the following specification and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a mammal's heart and circulatory system showingthe approximate configuration of the heart.

FIG. 2 is a schematic representative of how a mammalian heart workswithout regard to its configuration.

FIG. 3 is a schematic representation of how a cardiopulmonary machineworks.

FIG. 4 is a longitudinal cross-section view of a multichannel catheterof this invention showing the interrelationship between the majorportions of the invention.

FIG. 5A is a perpendicular cross-section taken along lines 5—5 of thelongitudinal axis of the device of this invention shown in 4A.

FIG. 5B shows a closely related configuration taken along line 5—5 ofFIG. 4 a.

FIG. 5C shows a slight modification of the cross-section taken along theline of 5—5 of FIG. 4.

FIG. 6 shows a cross-section of the longitudinal axis of a slightlydifferent configuration of the multichannel catheter of this invention.

FIG. 7 shows a perpendicular cross-section taken along lines 5—5 of FIG.4 and shows the size relationships between the various parts of themulti-channel catheter of this invention.

FIG. 8 is a perspective closeup of the distal end of the catheter ofthis invention showing an inflated balloon and elongate openings.

FIG. 9 is a side elevation closeup of the distal end of the catheter ofthis invention showing an alternative design for the elongate openings.

FIG. 10 is a side elevation closeup of the distal end of the catheter ofthis invention showing an alternative design of the openings.

FIG. 11 shows a cardiopulmonary system using the catheter of thisinvention.

FIG. 12 shows positioning the balloon at the distal end of the catheterin the ascending aortic by insertion through the aorta.

FIG. 13 shows positioning the balloon at the distal end of the catheterin the ascending aorta by insertion through the aorta near thesubclavian artery.

FIG. 14 shows a plan view of an embodiment of a catheter of theinvention including two balloons on the distal end of the catheter.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS

Description of the Catheter

Broadly, this invention is a multichannel catheter useful incardiovascular surgery, which allows a physician to

-   -   deliver extracorporeal blood to a patient undergoing        cardiovascular surgery,    -   occlude the flow of blood at the ascending aorta,    -   deliver cardioplegia fluid to the heart and    -   vent the left heart.

The multichannel catheter is of a diameter size to be inserted into theaorta or one of its major branches (e.g. a femoral artery) and used inopen chest surgery or in less invasive surgery. Alternatively, thecatheter is used in open chest surgery and inserted by cannulation atthe aorta or through one of the great arteries, e.g., thebrachiocephalic artery. The design of the blood flow configuration willdepend on where and how the catheter is to be inserted, as discussedhereinafter.

In general, the multichannel catheter of this invention comprises atleast 3 passageways,-with a large, central passageway to maximize theflow of oxygenated blood from a cardiopulmonary machine. An importantaspect of this invention is to maximize the flow of blood through thelarge channel while minimizing the outside diameter of the catheter andthus provide adequate systemic extracorporeal blood flow for the vastmajority of patients in which the catheter is used. Of the availablepassage space in the catheter of this invention at least about 70% isallocated to this large passageway to maximize the flow. Preferablyabout 80% and more preferably about 90% of the available passagewayvolume, is used for the flow of perfused blood to the arterial side of apatient in need of supplementary, extracorporeal blood circulation. Theother channels, at least two, comprise the remainder of the availablevolume (i.e., about 10%-30%) with each channel integrated into the wallof the large central passageway. Generally, the available volume isdetermined by calculating the area of a cross-section of eachlongitudinal passageway and multiplying by the length. Since the lengthis about the same in each case, the relative volume for each channelwill be directly proportional to the cross-sectional area of eachpassageway.

More specifically, the multichannel catheter has distal and proximalends and comprises a large central, first channel, i.e., a passageway orlumen. This channel extends substantially the length of the catheter,comprises at least about seventy percent of the available internalchannel volume of the catheter, and is closed at its distal end, but hascertain outflow openings for extracorporeal blow flow, as discussed ingreater detail hereinafter. The catheter has at least second and thirdchannels, each of which extends substantially the length of thecatheter, parallel to said first channel but independent thereof.Together, these additional channels comprise not more than about thirtypercent of the available internal channel volume of the catheter and areintegrated into the wall of the first channel. The second channel(generally the larger of the two smaller channels) is open at its distalend, while the third channel's distal end is in communication with aninflatable means. The catheter further has a plurality of openings nearthe distal end of said catheter communicating with said first channeland an inflatable means, i.e., a balloon, integrated into the distal endof the catheter between the first channel blood outflow openings andsaid second channel's distal opening. The openings are said to be“upstream” of the balloon, while the distal opening of the secondchannel are said to be “downstream” of the balloon. The interior of theinflatable means communicates with the distal end of the third channelthrough an opening in the wall of the catheter. The catheter is made ofphysiologically acceptable material and is of a size suitable forinsertion into a blood vessel of a mammal, particularly a human.Preferably, at least some and preferably the majority of the pluralityof openings communicating with the first channel are elongate in shapewith the length of the openings being substantially parallel to thelength of the catheter.

Turning now to FIG. 4, one can see a detailed representation of thecatheter of this invention which is a cross-sectional view of the lengthof the catheter. The catheter is shown generally as 30 having a proximalend 31 and a distal end 33. The large first channel 34 is defined by thewall 32 of the catheter. The second channel 36 and the third channel 38are shown as being integrated into the wall of the first large channel.The second and third channels are integrated with the wall 32 of thefirst channel 34 and are shown as having an interior wall portion 41defining the smaller second and third channels.

Toward the distal end 33 of the catheter 30 are located openings 40 thatare outlet ports for the fluid passing through the channel 34. In use,that fluid will be blood that is circulated to the arterial side of apatient in need of such extra-corporeal circulation. As will bediscussed in greater detail, hereinafter, the catheter of this inventionis preferably designed to be inserted into a femoral artery of a humanpatient and advanced sufficiently so that the distal end is positionedin the ascending aorta. Thus, the catheter must be flexible enough toreadily bend at its distal end as shown in FIG. 10, but it must also bedesigned to minimize kinking to avoid reduced fluid flow through thepassageways 34, 36 and 38 in FIG. 4. The openings 40 communicating withchannel 34 are located on the proximal side (i.e. upstream) of theinflatable means 42 (also referred to as the “balloon”) so that bloodflows out of channel 34 near the great arteries. While some of theopenings may be adjacent the balloon 42, preferably within about an inchof the proximal edge 44 of balloon 42, the openings 40 are located suchthat they do not contribute to kinking of the catheter as it passes theaortic arch. Thus the openings 40 are located in the distal portion ofthe catheter so that when the catheter is positioned as shown in FIG. 11the openings are in a region of the catheter that is relativelystraight. A few of the openings may be located immediately adjacent theproximal side of the balloon 42 (e.g., within about an inch of theproximal edge 44 of the balloon 42), while the majority will be proximalto the great arteries.

Alternatively if the catheter is used in open chest surgery, it can beinserted through the aortic arch as shown in FIG. 12 or through thebrachiocephalic artery 102 or one of its branches. In FIG. 12, the samenumerals are used in describing the catheter of this invention as areused in FIG. 4. Referring now to FIG. 12, the aorta is generally shownas 100 with the ascending aorta 101 and the great arteries shown as 102(brachiocephalic), 103 (carotid), and 104 (subclavian). In open-chestcardiovascular surgery, the catheter 30 is inserted at the ascendingaorta 101 to position balloon 42 snugly against the walls of theascending aorta 101. In this case, because the catheter 30 does not flexaround the aortic arch 105, there is not as much stress on the distalend 33 of catheter 30 and less likelihood of kinking. Thus numerousopenings 40 may be located closer to balloon 42 as to insure the flow ofblood to the aorta. The same is true of cannulation through one of thegreat arteries such as the brachiocephalic artery 102 or one of itsbranches. Another region of insertion may be near the subclavian artery104 through the aorta as shown in FIG. 13.

Whatever the insertion point of the catheter is, it is important thatthe total outflow capacity of the outlet ports 40 is greater than theinflow capacity of the blood flowing into the catheter. This will meanthat total collective cross-sectional area of openings 40 will exceedthe total cross-sectional area of channel 34. Thus, to calculate thecollective cross-sectional area of openings 40, one determines the areaof each opening and adds the area of each opening. Preferably the totalarea (i.e. outflow capacity) of the openings will exceed thecross-sectional area (i.e. inflow capacity) of channel 34 by at least afactor of 1.2. Having a factor of greater than about 2 is even morepreferable. For example, if the radius of channel 34 is 2.5 mm, thecross-sectional area is 19.6 (2.5×2.5×3.14=19.6) and the totalcross-sectional area of the openings 40 will be at least 23.6(1.2×19.6=23.6), more preferably 39.2 (2×19.6=39.2). Preferably, eachopening has a cross-sectional area of about 3-40 mm2, preferably about 5to about 20 mm². The total number of openings may be as few as 3 largeopenings up to about 20 openings of various shapes.

While-the shape of the openings 40 may be of any appropriate shape forthe outflow of blood, it is preferable that some, generally a majorityof the openings are elongate in shape. While the openings may bepositioned in any configuration at the distal end of the catheter, forexample, the longitudinal axis of the elongate openings may bepositioned substantially parallel to the length of the catheter or at aslight angle such that it forms a helical design or the length could beperpendicular to the length of the catheter. However, it is preferredthat the elongate openings have the length of the opening substantiallyparallel to the length of the catheter. The number of openings that canbe present may vary from 3 to 20 or more but must be placed in a mannerthat the structural integrity of the catheter is maintained. By havingelongate openings instead of circular openings the sheer stress on theblood is reduced by allowing the blood to flow out of the outlets moreeasily. In addition to the elongate openings located in the distalregion of the catheter other openings may be located further upstream ofthe elongate openings 40. Further designs may be seen in FIGS. 8, 9 and10. The design of the openings 40 may generally be that of an oval, arectangle, a trapezoid or some similar elongated design. In general,they will be approximately one cm to about four cm, preferably about 2.5cm long with a width at the broadest portion of the opening no more thanabout 5 mm. The openings 40 are positioned at the distal end of thecatheter so that when the catheter is positioned with the balloon 42 inthe ascending aorta, the openings are adjacent the great arteries sothat blood can flow more freely to the great arteries to ensure thenecessary oxygenation of tissues (i.e. perfusion) for the rest of thebody. By having a majority of (e.g., oval) openings and ensuring theoutflow capacity exceeds the inflow capacity the sheer stress on theblood passing through the first channel 34 will be significantlyreduced. By having the elongate openings at the distal end andmaximizing the size of channel 34, the flow rate through the largechannel 34 may be up to six liters (L) per minute without having adverseaffect on the blood due to too much shear stress on the red cells,platelets or white cells. Having the elongate openings and properoutflow capacity also reduces the pressure drop between the proximal endwhere the catheter is attached to the cardiopulmonary machine and theexit at the openings 40. Generally, the pressure drop will be under 300millimeters of mercury and preferably under 200 millimeters of mercury.The pressure drop can be further reduced by having additional holestowards the proximal end of the catheter but somewhere between themidpoint of the catheter and the distal end. This design is seen in FIG.10. As discussed, before the openings 40 will be positioned andconstructed to minimize the chance of kinking when the catheter passesover the curve of the aortic arch and generally will be sufficientlyproximal of the balloon 42 with the largest cross-section of openings tobe positioned in a section of the catheter that remains straight. While,a few (e.g., 2-4) small openings may be placed within about 2.5 cmproximal of the balloon 42, the majority are about 7.5 cm to about 30 cmon the proximal side (i.e., upstream) of the balloon, depending on thecatheter sizing for the patient.

In general, the maximum length of the multichannel catheter of thisinvention will be that length necessary to insert the catheter into thefemoral artery of the patient and moving it up the artery to place thedistal end having the balloon within the ascending aorta. Depending onthe size of the patient, whether a child or an adult, the length may befrom about 40 centimeters up to about 100 centimeters or more.Generally, the range will be about sixty to about one hundredcentimeters with about eighty-five centimeters being an average lengthsuitable for most people. The length will be significantly less whenused in open-chest surgery with aortic insertion or brachiocephaliccannulation.

The outside diameter of the multichannel catheter of this invention willbe such that it can be inserted and moved through the femoral artery ofthe patient and located in the ascending aorta as discussed above.Generally, this will have an outside diameter (OD) of no more than about30 French, preferably of about 18 to 24 French with about 20 to 22French outside diameter fitting most patients. The French scale is ascale used for denoting the size of catheters or other tubularinstruments, with each unit being roughly equivalent to 0.33 millimeters(mm) in diameter. For example, 18 French indicates a diameter of about 6millimeters while 20 French would indicate a diameter of about 6.6millimeters. The thickness of the wall 32 may be between about 0.2 mm toabout 1.0 mm. Thus, the inside diameter of channel 34 will generally notexceed about 28.2 French, and may vary from about 14.8-22.5 French.

By using the multichannel catheter of this invention, which is designedto maximize the flow of blood within the large channel while minimizingthe outside diameter of the catheter, the peripheral flow of blood tothe extremities, i.e., the arms and legs is significantly improved overany known commercial catheter designs. This is thought to be due notonly to the improved blood flow through the catheter and out theopenings, but also to the smaller outside diameter of the catheter andflow of blood back down the femoral artery around the catheter.

In some cases, it may be preferable to provide the multichannel catheterof this invention with a distal end that has a slight “preshaped” regiondesigned into it. The preshaped region is designed to correlate to theaortic arch. In inserting the catheter the preshaped region ismaintained in a relatively straight condition by using a stylet, i.e., astiff plastic support mechanism positioned in channel 34. This can beused in conjunction with a guide wire positioned in channel 36. When thedistal end of the catheter reaches the curve of the aortic arch, thecatheter continues to be advanced via the femoral artery, but the styletis slowly withdrawn allowing the precurved region to bend around theaortic arch to have the balloon then located past the brachiocephalicartery but before the coronary ostia.

As shown in the FIG. 4, at the distal end of the catheter of thisinvention there is located a inflatable means 42 which in general is aballoon that is attached to the distal end of the catheter. The interiorof the inflatable means is in fluid communication with the third channel38 so that the balloon can be inflated or deflated by transporting fluidthrough the channel to the balloon to inflate it or sucking the fluidout to deflate the balloon. The design of the balloon may be any designknown in the art, such as that shown in U.S. Pat. Nos. 5,423,745;5,516,336; 5,487,730; and 5,411,479, the pertinent parts of which areincorporated by reference. Other useful balloon components arecommercially available to one of ordinary skill. While one balloon isshown in FIGS. 4 and 8-13 multiple balloons could be used, e.g., two.However, for ease of use and preparation, one balloon is preferred. Itis also preferred that the distance between the proximal edge 44 of theballoon and the distal side 45 be such that the surface contact with theinterior wall of the ascending aorta wall be maximized. This helpsensure a tight seal to prevent leakage. This distance between 44 and 45may be from about 20 mm to about 50 mm, preferably about 30 mm to about40 mm.

The second channel 36 is designed to introduce a cardioplegia solution,to evacuate fluid (i.e., vent the left ventricle), or to carry aguidewire or various types of probes or for treating the heart. Thus, ithas at least one opening 37 at the distal end 33 of catheter 30downstream of balloon 42. This allows a cardioplegia solution or theappropriate fiberoptic cable to be inserted into the channel and movedthrough the channel out exit 37. It also allows for a negative pressureto be applied to vent the left ventricle of the heart.

In a preferred mode of operation, the catheter of this invention isinserted percutaneously or by cutdown into the femoral artery of apatient and is threaded through the femoral artery to the ascendingaorta to be positioned there. Occasionally, it may be necessary tosupplement the flow of a patient's heart if it has been weakened, andthis can be done by flowing oxygenated blood through the centralpassageway 34 out the outlets 40 to the great arteries and otherarteries in the arterial system. If an operation is to be performed onthe heart, which requires arrest of the heart, the catheter ispositioned appropriately, the balloon is inflated to block the flow ofblood into the heart from outflow openings 40. Cardioplegia solution isadministered through channel 36 out opening 37 to arrest the heart andblood is circulated through channel 34 out openings 40 to maintaincirculation of oxygenated blood in the patient during the operation.

Turning now to FIGS. 5A through 5C and FIG. 6, one can see across-sectional view taken along lines 5—5 in FIG. 4. In these figures,it can be seen that the large central passageway 34 is defined by thewall 32 of the overall catheter and that the channels 36 and 38 areintegrated into the wall 32. They may be integrated so that they arepositioned more interiorly as shown in FIG. 5A or more exteriorly asshown in FIG. 5B with cross-sectional diameters that are essentially acircle. On the other hand, in FIG. 5C, the cross-sectional of channels36 and 38 may be elongated or oval. While the relative volumes of thetwo are shown to be about equal, the total volume of flow available forall passageways 34, 36 and 38 is divided as follows. The amount of fluidflowing through passageway 34 will be at least about seventy percent ormore (e.g., up to about 90%) in order to achieve the advantages of thisinvention with the flow through passageways 36 and 38 being theremaining thirty percent or less (i.e., down to about 10%). In general,there will need to be less volume in the channel for communicating withthe balloon than in the channel that is available for the cardioplegiaor the fiberoptic instruments or cable. While generally, it ispreferable to have the channels 36 and 38 opposed one hundred eightydegrees from each other as shown in FIGS. 5A to 5C, it may be possibleto have them adjacent as shown in FIG. 6. Having them adjacent makes thepreparation a bit more difficult than having them opposed as in FIGS.5A, 5B and 5C.

The ratio of the total volume of the cardioplegia channel 36 to theballoon inflating channel 38 will vary from about 1:1 to about 4:1. So,for a multichannel catheter in which about 70% of the total availablevolume is provided for the channel 34 and about 30% of the totalavailable volume is provided for channels 36 and 38, channel 36 willaccount for about 15% to about 24% with channel 38 accounting for about15% to about 6%. Alternatively if channels 36 and 38 collectivelyaccount for about 10% of the total available volume then channel 36 willhave about 5% to about 8% while channel 38 will have about 5% to about2%.

By referring to FIG. 7, one can see the relative proportions of thethree channels of the multi-channel catheter of this invention. In theFigure the abbreviations have the following meanings:

-   -   ID—inner diameter    -   OD—outside diameter    -   IWT—inner wall thickness    -   OWT—outer wall thickness        Summarizing the dimensions, they are as follows:    -   OD 32:16-30 French (5.3-9.9 mm)    -   ID 32:14.8-28.2 French (4.7-9.3 mm)    -   OWT 32:0.6-1.0 French (0.2-0.3 mm)    -   IWT 41:0.6-1.0 French (0.2-0.3 mm)    -   ID 38:0.6-1.0 French (0.2-0.3 mm)    -   ID 36:0.6-4.0 French (0.2-1.3 mm)

The catheter of this invention is able to handle a blood flow ratethrough the central channel 34 of about one-half up to about 6 litersper minute with the proper sizing and design. Generally, a flow of about5 liters per minute is sufficient to handle the vast majority ofcirculatory needs required by patients having heart surgery performed.On the other hand, the flow of cardioplegia solution or drug-containingsolution through channel 36 is-generally about 100 to about 300 cubiccentimeters (0.1-0.3 liters) per minute. The balloon inflation channel38, which is generally smaller than channel 36, will be of a sizesufficient to carry balloon-inflating fluid, e.g., saline, to theballoon. The volume of the balloon is generally about 40 cc to about 100cc, generally about 60 cc. Thus, channel 38 is of a size sufficient tocarry that volume over a short period of time, i.e., less than a minuteand generally less than about 10 seconds. The volume of the balloon willbe greater if the distal end of the multichannel catheter is tapered inthe region covered by the balloon.

In general, the catheter of this invention will need to be flexibleenough to easily be inserted up through the femoral artery to bepositioned in the ascending aorta. The flexibility needs to besufficient so that the catheter can bend but will not kink at bodytemperature. In general, this flexibility is measured by Durometer andwill be somewhere in the 55 to 65 range. Generally, we will have aDurometer reading of about 60. It is preferable that the distal endwhere the balloon is located is somewhat stiffer than the rest of thecatheter. This helps to ensure the positioning of the balloon in theascending aorta to ensure that it does not get displaced during theoperation.

Turning now to FIGS. 8-10, one sees a closeup of the distal end 33 ofcatheter. It should be understood that the figures are representative,but are not necessarily drawn to scale. This is an external view thatshow the elongate openings 40 and the balloon 42 in its inflated form,although not fully inflated. In general, the balloon is preferably of anoblong shape as shown in FIG. 8. This maximizes the surface contact withthe ascending aorta wall and minimizes the stress on the vessel wall bydispersing the pressure over a greater area. By maximizing the surfacecontact, the position is maintained to a greater extent. While thesurface of the balloon may be smooth, as shown in FIG. 10, it preferablyhas a design on it that provides additional friction between the balloonsurface and the internal surface of the aortic arch. Thus the balloonsurface may have either depressions, as shown in FIG. 8, or ridges, asshown in FIG. 9, in a design that helps maintain the balloon inposition. It is preferable to have on the surface of the balloon certainridges or bumps indicated in FIG. 9 as 43 to provide additional frictionfor maintaining the position of the balloon in place and minimizing thedisruption of plaque that may be present. Generally, the volume of theballoon will be about 30 to about 100 cubic centimeters, preferablyabout 60 cc. The length of the balloon from its proximal end 44 to itsdistal end 45 will generally be about 2.5 cm to about 7.5 cm with about4 cm being optimal. It will need to expand sufficiently to block theascending aorta completely so that blood does not get to the arrestedheart from the cardiopulmonary machine. “FIG. 14 shows an embodiment ofa catheter of the invention including two balloons on the distal end ofthe catheter.”

In performing open heart or least invasive cardiac surgery, generally,it is necessary to do an angiogram by placing an angiogram catheter upthe femoral artery and positioning it in the ascending aorta. Based onthe length of the angiogram catheter balloon placement position can bedetermined, the multi-channel catheter of this invention has markingsindicating its length measured from the distal end to various distancesnear the proximal end so that the physician knows exactly how far toinsert the catheter of this invention. Having that information indicatedon the catheter makes it easier for the physician to do the insertionand also reduces the need to use fluoroscopy to properly insert thecatheter. On the other hand, if a angiogram catheter measurement is notdone before inserting the catheter of this invention, an ultrasoundprobe may be used to position the catheter of this invention where thecatheter of this invention carries a detectable beam on the tip of thecatheter. Alternative methods may be employed for positioning thecatheter, such as guidance by fluoroscopy or echocardiography,fiberoptic visualization through the catheter, magnetic or electronicguidance, or other means of insuring proper placement.

The material which is used to manufacture the multichannel catheter ofthis invention may be any material that is physiologically acceptable,that is it is made of a material that will not have an adverse effect onthe patient when used in the manner in which it is intended. Generallythis will require the use of biocompatible material (i.e. the body willnot react with it) for preparing the catheter of this invention. Inaddition, the material that is used must possess sufficient stabilityand flexibility to permit its use in accordance with the process of theinvention. Various biocompatible polymers may be used. A polymer that isparticularly valuable for preparing the catheter of this invention ispolyvinyl chloride (PVC) blood tubing, that has been plasticized.Preferably the plasticizer which is used in the PVC is trioctyltrimellitate (TOTM) while the standard plasticizer di-(2-ethyl hexyl)phthalate (DEHP). TOTM plasticizer is less extractable than DEHP andproduces a better blood response. Suitable PVC resin is available fromDow Chemical Corp., Midland, Mich., or Polymer Technology Group (P.T.G.)Inc., Emeryville, Calif. Another polymer that is useful for preparingthe multichannel catheter of this invention is medical gradepolyurethane. Other polymers may be prepared based on a family ofpolysiloxane-containing copolymers termed surface modified additions(SMAs). These copolymers may be blended with the base polymer beforeprocessing or coated on the blood contacting surface. When blended withthe base polymer the SMA will migrate to the polymer surface resultingin a high concentration of the SMA of that surface, which has feweradverse reactions with the blood that contacts it. When coated, devicesurfaces are pure SMA. High surface concentration of the SMA areresponsible for the improved biocompatibility of extracorporeal circuitcomponents. Plasticized PVC is particularly useful as the base polymer.A further description of these polymers is given in article entitled“Surface Modifying Additives for Improved Device-Blood Compatibility”from ASAR Journal 1994 M619-M624 by Chi-Chun Tsai et al. The article isincorporated herein by reference. Such polymers are available fromP.T.G. Corp.

Other useful polymers include polyurethane-urea biomaterials that aresegmented polyurethane (SPU) some of which have surface-modifying endgroups (SMES) covalently bonded to the base polymer. These are describedby Ward, et al. in an article entitled “Development of a New Family ofPolyurethaneurea Biomaterials” in Proceedings From the EighthCimtec—Forum on New Materials Topical Symposium VIII, Materials inClinical Applications, Florence, Italy, July, 1994. See also U.S. patentapplication Ser. No. 08/221,666, which is incorporated herein byreference.

Sometime the blood interacts with artificial surfaces of polymers insuch a way that the blood coagulates on the surface creating thrombi.These thrombi can block the catheter or blood vessels, preventing theblood from flowing and causing oxygen depletion and nutrient starvationof the tissues. Thus the surface of the polymeric material used for themultichannel catheter of this invention should not give rise to thrombusformation. An anti-thrombotic agent can be used to prevent the clotsfrom forming. Some of the blood polymer interactions are discussed inarticle entitled “Biomaterials in Cardiopulmonary Bypass” found inPerfusion 1994; 9:3-10 by James M. Courtney et al.

Polymer modifications that permit an improvement in blood compatibilitywhile maintaining acceptable levels of other fundamental propertiesinclude the treatment of surfaces with protein, the attachment ofanti-thrombotic agents and the preparation of biomembrane-mimeticsurfaces. The preferred anti-thrombotic agent is the anti-coagulantheparin which can be attached ionically or covalently. Preferably it isattached covalently.

An additional factor to consider in preparing the catheter of thisinvention is the relative roughness of the blood-contacting surface.Excess surface roughness has deleterious effects on blood flow throughthe catheter and should be avoided.

Another article that discusses the factors relating to compatibility ofsurfaces contacting blood is entitled “State-of-the-Art Approaches forBlood Compatibility” from Proceedings of the American Academy ofCardiovascular Perfusion Vol. 13, January 1992, pages 130-132 by Marc E.Voorhees, et al.

Use of the Catheter of This Invention

The catheter of this invention may be used in several different ways.For a condition in a patient that needs supplementary extracorporealblood circulation because of insufficient circulation from his or herown heart, the catheter may be introduced via a femoral artery,positioned as appropriate and attached to a cardiopulmonary bypassmachine to circulate blood through the large central channel 34 and outopenings 40. When appropriately positioned with the distal end of thecatheter in the ascending aorta, a fine fiber optic cable may bethreaded through second channel 36 to examine the aortic area of theheart. If it is determined that a heart operation is necessary, theballoon may be inflated through channel 38 to block the ascending aorta,cardioplegia solution may be administered through channel 36 to arrestthe heart, and oxygenated blood from a cardiopulmonary machine is pumpedthrough channel 34 and openings 40 into the arterial pathway of thepatient's circulatory system. Thus, the device of this invention may beused in cardiovascular surgery in general or various heart examinationsor treatments of artery and valvular disease. Cardiovascular surgery ismeant to include surgery to the heart or to the vascular system of apatient. The catheter is particularly useful in cardiac surgery, whetheropen chest surgery or minimally invasive heart surgery. Such surgery mayinclude, but are not limited to, the following:

1. Coronary artery revascularization such as:

-   -   (a) transluminated balloon angioplasty, intracoronary stenting        or treatment with atherectomy by mechanical means or laser into        the coronary arteries via one lumen of the catheter or    -   (b) surgical mobilization of one or both of the mammary arteries        with revascularization achieved by distal anastomoses of the        internal mammary arteries to coronary arteries via a small        thoracotomy.

2. Any atrial or ventricular septal defect repair such as by

-   -   (a) “closed” cardioscopic closure or    -   (b) closure as in “open” procedure via a thoracotomy or other        limited access incision.

3. Sinus venosus defect repair similar to above.

4. Infundibular stenosis relief by cardioscopic techniques.

5. Pulmonary valvular stenosis relief by cardioscopic techniques.

6. Mitral valve surgery via thoracotomy.

7. Aortic stenosis relief by the introduction of instrumentation via alumen in the aortic catheter into the aortic root.

8. Left ventricular aneurysm repair via a small left anteriorthoracotomy.

A significant advantage of the unique multichannel catheter of thisinvention is its ability to be adapted to be used in accordance with theneeds of a patient. For example, a patient with symptomatic coronaryartery disease undergoes a diagnostic evaluation to determine the typeof treatment that best suits that patient's condition. As a result ofthe evaluation, the physician may recommend surgical treatment,interventional cardiology treatment or some alternative treatment.Interventional treatment may include percutaneous transluminal coronaryangioplasty, atherectomy or the use of a stent to keep the vessels open.Alternative treatment may include the use of a laser or myoplasty.

If additional treatment is recommended, the multichannel catheter ofthis invention is particularly valuable in the further evaluation todetermine the condition of the patient,the type of treatment recommendedand the type of drugs that might be useful to administer to the patient.Thus, in using the multichannel catheter of this invention, the catheteris inserted into a femoral artery by percutaneous puncture or directcut-dow. The distal end of the catheter, which carries the balloon, isinserted first and moved through the femoral artery to be positioned inthe ascending aorta as discussed in more detail hereinafter. Initially,the physician performing the work may wish to introduce instrumentsthrough the channel (36 in FIG. 4) or other probes to allow observationor measurement of the internal condition of the artery, aortic archand/or aortic semilunar valve. A cardioscope, an electrophysiologyprobe, a transmyocardial revascularization probe, a radiation probe, orthe like may also be inserted through channel 36. Once observations aremade concerning the condition of the heart and associated arteries, thephysician can then take additional steps. For example, it may bedesirable to administer a biologically active fluid directly to theheart or aorta using an appropriate liquid composition containing anactive entity appropriate for the patient's condition. The activeentities in such a biologically active fluid include drugs (particularlythose having cardiovascular effect) that are pharmaceutically acceptablesmall organic molecules, small polypeptide molecules, larger polypeptidemolecules, and even a DNA or RNA that may be useful for gene therapy.Examples of useful molecules include those useful as antianginals (e.g.,organic nitrates, calcium channel blockers, β-adrenergic antagonists)antihypertensive, antiarrhythmics, antihyperlipoproteinemias, myocardialcontractile enhancers, anti-atherosclerotic agents, and the like. Suchfluids especially for cardioplegia can best be delivered through channel36 in FIG. 4, but alternatively can be delivered in the fluid used toinflate balloon 42 through channel 38 in FIG. 4. In the latter case, thematerial used for the balloon would be semipermeable to allow the drugto diffuse through the balloon membrane. A drug having lipid-dissolvingcharacteristics can be delivered through the balloon membrane.Alternatively, it may be useful to deliver such an active agent byadding it to the cardiopulmonary machine reservoir.

Once the catheter is in place, and observations regarding the internalconditions have been made, the physician then can move on to the nextsteps. For example, least invasive surgery, as discussed in U.S. Pat.No. 5,452,733, may be performed on a beating heart with no initialcardiopulmonary support, i.e., no blood would flow through the wouldcontinue to function. If at any time, the physician would decide thatcardiopulmonary support would be needed, supplemental blood flow from acardiopulmonary (heart/lung) machine could be started and work could becontinued with a beating heart or a fibrillating heart. Once a decisionis made to completely arrest the heart, cardioplegia solution isdelivered to the heart through the channel 36 after balloon 42 isinflated to block the flow of blood to the heart from thecardiopulmonary machine. As described, the multichannel catheter of theinvention can be used in least invasive surgical procedures as well asopen chest surgery.

The multichannel catheter of this invention is particularly useful inperforming heart surgery where the heart is arrested using acardioplegic solution and blood is circulated to the patient via acardiopulmonary bypass machine. In this case oxygenated blood iscirculated through the large channel of the catheter of this invention.The introduction of negative pressure on the venous drainage system maybe used to enhance venous drainage and reduce the need to vent the rightside of the heart. Generally, the negative pressure may be maintained atthe vena cavae regions (superior and inferior) using a centrifugal pumpattached to a standard femoral venous cannula. A system for performingsuch a process is depicted in FIG. 11.

In general, the process for performing surgery on a mammal's heartcomprises a sequence of steps. A single femoral access cannula isinserted into the mammal's femoral vein to position it so the distalopen end of the cannula is adjacent the vena cava region of the mammal'sheart and the proximal end of the cannula is attached to acardiopulmonary bypass machine through a centrifugal pump wherein thecardiopulmonary bypass machine comprises a blood oxygenation meansfluidly connected to the centrifugal pump. At about the same time amultichannel catheter of this invention is inserted into a femoralartery.

The multichannel catheter is positioned within the subject's bloodcirculatory system such that the distal end of said catheter ispositioned in the ascending aorta such that the first channel openingsare located near the great arteries, the inflatable means is located onthe cephalid side of the aortic valve and the distal end of the secondchannel is located proximate the aortic valve and downstream of theinflatable means.

Next, a source of oxygenated blood from the cardiopulmonary machine isconnected to the proximal end of said first channel of the catheter anda source of cardioplegia fluid is connected to the proximal end of saidsecond channel. A source of fluid is connected for inflating saidinflatable means to the proximal end of said third channel and theinflatable means is inflated to block the flow of blood to the heart.

Cardioplegia solution is pumped into the heart to arrest the mammal'sheart and oxygen-rich blood is pumped through said first channel out thefirst channel openings upstream of the balloon at rate sufficient tomaintain the subject's metabolism and perfusion while at the same timeoxygen-depleted blood is removed from the mammal's vena cavae regionsthrough the femoral vein cannula by applying a negative pressure usingthe centrifugal pump. The physician can then perform a surgicaloperation on the heart as needed and said subject is maintained asneeded.

Referring to FIG. 11, the femoral vein is accessed percutaneously or bycut down using the appropriate size standard femoral access cannula 50(such as an Research Medical Inc. #TF-030-050). This cannula conductsde-oxygenated venous blood from the vena cava 51 to PVC tubing 52 (e.g.0.5 inch inner diameter). This tubing is attached to the negativepressure (inlet) port 53 of a centrifugal pumping device 54 (such as theSt. Jude Medical #2100CP); the positive pressure (outlet) port 55 of thecentrifugal pumping device is connected via tubing 56 (0.5 inch ID PVC)to a venous reservoir system 57 (such as the COBE Cardiovascular, Inc.VRB 1800). This configuration pulls blood from the vena cava 51 to thevenous reservoir 57. Utilization of negative pressure in this manner toprovide venous blood return eliminates the need to “vent” or empty theright heart. By using a centrifugal pump that reaches about −20 to about−50 mm of mercury (mm Hg), a sufficient negative pressure is maintained.The use of a closed reservoir system is preferred to eliminate air/bloodinterface and associated blood trauma. The venous blood exits thereservoir through tube 58 (e.g. ⅜ inch ID PVC tubing). This tube isconnected to an oxygenator/heat exchanger means 59 (such as the COBECardiovascular, Inc. model #CML DUO #050-257-000) to oxygenate theoxygen-depleted blood. The blood will be pumped through themembrane/heat exchanger by a roller pump device 60 (such as the COBECardiovascular, Inc. model #043-600-000). The oxygenator will oxygenatethe blood and the heat exchanger will regulate blood temperature. Theoxygenated arterial blood will exit means 59 through tube 61 (such as ⅜inch ID tubing), pass through an arterial filter 62 (such as a COBECardiovascular, Inc. Sentry #020-954-000) and be delivered into thefemoral artery via the invention multichannel catheter 63. Preferably,all blood contact components are surface modified to reduce bloodtrauma, patient inflammatory response and requirements for patientanticoagulation.

The invention femoral artery catheter 63 provides flow of oxygenatedblood to the aorta 64. The invention catheter 63 is introduced into thefemoral artery 65 percutaneously or by cut down. The invention catheter63 is introduced utilizing a guidewire and stylet. The stylet providesstability to the catheter allowing the device to resist kinking duringinsertion with a minimum required wall thickness of the catheter.Accurate positioning of the balloon will differ from other positioningmethods by utilizing measurement of the cardiac. catheterizationcatheter. The appropriate distance will be determined and indicated onthe femoral artery catheter 63 prior to insertion; the distanceindicator markings 66 will provide simple and accurate balloonpositioning. Accurate positioning of the balloon tip may also beenhanced or verified using visualization by transesophogial echo orfluoroscopy.

The invention catheter provides a flow of oxygenated blood to the aortaas part of the cardiopulmonary bypass process. The catheter is of alength sufficient to extend from the insertion point in the femoralartery to the ascending aorta as shown in FIG. 11, which length willvary depending on the size of the patient, as discussed hereinbefore.The catheter has a proximal end 74 and a distal end 75. The catheter hasan inflatable balloon 76 located on the proximal side of the distal tipfor fixing the catheter within the ascending aorta. A channel extendsthe length of the catheter to the balloon with an outlet port thatcommunicates with the balloon so that the balloon can be filled with afluid from a syringe-type inflation device 73 to occlude the ascendingaorta as discussed herein. The catheter also has (a) a channel extendingfrom the proximal end 74 to outlet ports 77 upstream of the balloon fordelivering oxygenated blood and (b) a channel extending through theentire cannula with an outlet port 78 in the distal tip for a guidewireand/or delivering a cardioplegia solution to the heart through stopcock68 into inlet port 67 and line 69. Changing the position of the valve instopcock 68 to connect with line 70 and providing a negative pressure byroller pump 72, allows for the venting of the left ventricle by pullingfluid from the left ventricle through the semilunar valve throughopening 78.

Another aspect of this invention may be viewed as an improvement in theprocess of minimally or “least” invasive heart surgery. For traditionalopen heart surgery, the surgeon is required to make a long incision inthe front of the chest and divide the sternum bone to gain access forthe procedure. In minimally invasive heart surgery, a series (4-7) ofsmall incisions are made and the operation is carried out through narrowtubes or ports, using direct or video assisted visualization. Such aminimally invasive process and associated techniques are described invarious aspects in U.S. Pat. Nos. 5,433,700; 5,458,574; and 5,452,733,all of which are incorporated by reference in their entirety.

Another aspect of this invention is the overall management of coronaryartery disease management using the scheme outlined as follows, in whichthe multichannel catheter is used in the diagnostic evaluation andensuing treatment, particularly the surgical treatment. Generally, themanagement is a combination of preventative care, treatment andfollow-up and can be diagrammed as follows:

How to Make the Catheter

Generally the multichannel catheter of this invention is prepared usingany technique that provides the multichannel catheter herein described.The key is to ensure that the second and third channels are integratedinto the wall of the first channel. This may be done by forming thechannels separately then conjoining them, i.e. by gluing or other means.However, the multichannel catheter may be made through a mandrel-dippingtechnique, or preferably a continuous extrusion process. Extrusioninvolves forcing a fluid polymer material (as discussed above) through asuitably-shaped die to produce the cross-sectional shape, such as thatdepicted in FIGS. 5A, 5B, 5C and 6 or other suitable shape as describedherein. The extruding force may be exerted by any standard means knownin the art such as by a piston or ram or by a rotating screw, whichoperates within a cylinder in which the polymeric material such as PVCor polyurethane is heated and fluidized. The fluid material is thenextruded through the die in a continuous flow. The extrusion head willhave a multitubular die to provide a continuous multichannel catheter,essentially as described herein. Using a mandrel-dipping technique, amandrel having the desired size and cross section design is dipped in ordrawn through a fluid polymeric material so that the mandrel is coatedwith the polymer. The polymer is then dried on the mandrel and removedto give the desired design. This technique may be done at commercialmanufacturers, e.g., PTG, Emeryville, Calif. and others.

Once the multichannel catheter is formed, whether by extrusion ormandrel-dipping, it is cut to suitable lengths and treated to providethe further characteristics of the product to make it operable. Suchtreatment may occur in any particular order. For example, a plurality ofopenings (40 in FIG. 4) are formed near the distal end of said cathetercommunicating with said first channel. These openings are made inconformance with the designs discussed herein, and thus are preferablyelongate in that the longitudinal axis of the elongate design may behelical or orthogonal, but is preferably substantially parallel to thelongitudinal axis of the catheter itself. The openings may be providedby suitably cutting or punching the elongate design into the wall of thecatheter. The design is approximately oval, rectangular, or the likewith the length of the opening being about a size discussed hereinbefore. The width of the opening will be such it will not weaken thestructural integrity of the distal end of the catheter. FIGS. 8, 9 and10 present various configurations for the positioning of openings 40.Optionally, additional openings communicating with the first channel maybe provided along the length of the catheter positioned betweenapproximately the middle of the catheter and the elongate openings nearthe distal end. The openings are useful in reducing the pressure dropbetween the proximal end of the catheter and the distal openings to helpreduce the sheer stress on the blood.

In addition to the openings that communicate with the first, largechannel, at least one opening communicates with the third channel.Thereafter, an inflatable means, i.e. a balloon device, is integratedinto the distal end of the catheter such that the interior of theballoon communicates with the outlet of the third channel to allow fluidto flow through the third channel and to the interior of the inflatablemeans. In general, this may, be integrated by positioning a balloonhaving an opening corresponding to the opening to the third channel andadhering the balloon to the distal end of the catheter between theopenings to the first large channel of the catheter and the distal tipof the catheter. This adherence may be performed by using a suitableglue, solvent bond, light sensitive weld, or other suitable means knownin the art for this purpose. The material used for the inflatable meansmay be any suitable biocompatible material that is capable of beinginflated and deflated a plurality of times. Polyurethane-basedbiocompatible polymers are preferred. These are described in theaforementioned article by Ward, et al.

Finally, the distal end of the first, large channel and the third, smallchannel are closed. This may be achieved by plugging, solvent sealing,heating or other suitable means. The process must be carried out in sucha way that the distal end of the second channel remains open.

Having now described in detail how to make and use the catheter of thisinvention, the following non-limiting example is provided to furtherexplain important concepts of the invention. The example is to beinterpreted as representative but not limiting the scope of coverage ofthis patent application.

All references to any patents or articles in this application are to beinterpreted to specially incorporate each in this application byreference.

EXAMPLE 1

This Example shows the importance of the second and third channels,i.e., smaller channels 36 and 38 in the Figures, in the multichannelcatheter bearing integrated into the wall of the larger channel and theimportance of a significant outflow capacity in the outlet ports tominimize the pressure drop as the flow rate increases through the largechannel.

In this test ⅜″ inside diameter PVC tubing was used as a channel forstandard saline solution. The flow rate through the various tubes wasvaried from 0.5 to 6 liters per minute. The saline was pumped from afirst canister to a second using a roller pump. Tubes 1-6 havingslightly different designs were used in the test as follows:

-   -   Tube #1: This had two tubes of a much smaller outside diameter,        i.e., about ⅛″ and about {fraction (1/32)}″) within the length        of large passageway that were not integrate dinto the wall of        the ⅜″ tube. It had 3 circular outlets of about 2 mm diameter at        its distal end adjacent the balloon.    -   Tube #2: This was similar to #1 except it had 3 slightly larger        oval outlets of about 2 mm by about ¾″ in. (about 20 mm)    -   Tube #3: Same design as #2 with 5 additional circular distal        outlets of about 2 mm diameter each.    -   Tube #4: Same design as #2 with 10 additional circular distal        outlets of about 2 mm diameter each.    -   Tube #5: Same design as #2 with 15 additional circular distal        outlets of about 2 mm diameter each.    -   Tube #6: Same design as #1 without the interior tubing.

The pressure drop was measured by pressure manometer gauge prior to thecatheter. The saline was pumped through the catheter starting on theproximal end and flowing out the distal end through the outlet ports.Table I shows the results of the test. It clearly shows the importanceof not having any interior lines that are not integrated into the wallof the large catheter. The pressure drops at all flow rates are muchless for design #6 (more than 50%). Also when the outflow capacityincreases the pressure drop decreases, thus placing less stress on thefluid.

TABLE I Pressure Drop Flow #1 #2 #3 #4 #5 #6 Rate 0 0 0 0 0 0 .5 32 3230 20 20 21 1 51 51 51 49 49 30 1.5 74 74 65 65 59 58 2 109 105 89 89 8442 2.5 148 140 120 120 110 49 3 195 190 158 158 147 62 3.5 250 238 192192 178 82 4 300 286 231 231 216 97 4.5 354 335 270 265 251 119 5 450430 380 370 350 148 6

1. A single multichannel catheter useful for delivering extracorporealblood to a mammalian patient in need thereof wherein the catheter hasdefined length and available channel volume with distal and proximalends and comprises: at least three independent channels and anexpandable balloon at one end of the catheter, a first largest channeldefined by a surrounding wall and of a size to allow delivery of anamount of blood to the patient that is sufficient to support thepatient's metabolism and perfusion throughout the delivery of blood tothe patient, a second channel, smaller than the first channel andintegrated into the wall of the first channel, the second channelsuitable for (a) drug delivery to the heart, (b) accepting accessorysurgical devices and providing a pathway for the accessory surgicaldevices to the heart, and (b) venting the left heart, a third channelalso smaller than the first channel and integrated into the wall of thefirst channel, the third channel is suitable for delivery of a fluid tothe balloon for its expansion when positioned in the ascending aorta toocclude the flow of blood to the heart from the first channel, andwherein a plurality of openings for the outflow of blood, all of whichare located in the wall of the catheter, communicate only with the firstchannel, and a removable insertion stylet configured to be receivedwithin the first channel, whereby the insertion stylet prevents bloodfrom entering the first channel until the insertion stylet is removed.